Continuous clarification-filtration method

ABSTRACT

TO BE REMOVED THEREFROM, SAID MATTER BEING SELECTED FROM THE GROUP CONSTISTING OF FLOC, FIBERS, PARTIALLY OR TOTALLY FORMED FLOC, AND PARTICALLY OR TOTALLY FLOCCULATED FIBERS, SAID METHOD COMPRISING THE STEPS OF: 1. INTRODUCING INTO SAID LIQUID A FLOW OF GAS BUBBLES HAVING CONTAINED WITHIN THE INDIVIDUAL BUBBLES AT LEAST ONE POWDERED CHEMICAL PARTICLE HAVING AN ELECTRICAL CHARGE OF THE OPPOSITE POLARITY AS THE MATTER TO BE REMOVED FROM THE LIQUID TO BE CLARIFIED, SAID POWDERED CHEMICAL ALSO BEING A FLOCCULATING AGENT FOR THE MATTER TO BE REMOVED IN THE EVENT SAID MATTER TO BE REMOVE IS NOT OTHERWISE FLOCCULATED; 2. PROVIDING MEANS TO INSURE UNIFORM MIXING OF SAID GAS BUBBLES THROUGHOUT SAID LIQUID TO BE CLARFIED; AND   3. SUBSEQUENTLY REMOVING FROM THE SURFACE OF SAID LIQUID THE CONGLOMERATE FORMED BY ADHERENCE OF SAID NOW FLOCCULATED MATTER TO BE REMOVED FROM SAID LIQUID WITH THE POWDERED CHEMICALS INTRODUCED INTO SAID LIQUID IN SAID GAS BUBBLES, THUS LEAVING A CLARIFIED LIQUID BEHIND.

210-706 5;; 5 5 H SEARCH ROOM E37" Jan. 28, 1975 R. N. SILVA Re. 28,323

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Jan. 28, 1975 R. N. SILVA Re. 28323 CONTINUOUS CLARTF'ICATION-FILTRATIONMETHOD Original Filed Oct. 7, 1968 2 Sheets-Sheet z FIG. 4

IN VEN TOR.

United States Patent Int. Cl. B031! 1/00 US. Cl. 210-44 4 Claims Matterenclosed in heavy brackets [1 appears in the original patent but formsno part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

ABTRACT OF THE DISCLOSURE Method and apparatus to improve the adhesionbetween the air or gas bubbles used in a flotation clarifier and the docalready formed with the use of one or more chemicals or coagulant aids,by adding the necessary electrical charge to said air or gas bubbles inorder to make them adhere more efficiently to said floc.

This invention relates to clariliers, and more particularly relates toflotation method and apparatus which I call continuousclarification-filtration because of its good performance, and isintended to be applied to clarify sugar solutions but it can be used forclarifying any liquid. In the past, it has been customary in flotationpractice to aerate the liquid being treated without taking care of theelectrical charge of the air or gas bubbles which were supposed toadhere to the floc, fiber, etc., being floated. However, many times itwas found that the air or gas bubbles did not adhere to the floc, fiber,etc., as expected, but passed upward until reaching the liquid levelwithout even touching the doc, fiber, etc. Various methods have beendevised to counteract these conditions. The use of coagulants andpolyelectrolytes have been solving the problem up to the present, butits wide use in this field have never been a definite help.

Besides it has been found that even though a successful lab test couldbe made with a liquid, perfectly floating its floc, fiber, etc., whenthe same liquid is tried in a larger scale, adding the same proportionof flocculating aid if required, not'always do the air or gas bubblesadhere to the doc, fiber, etc., as the lab test did. The above be haviorshows that a change in the electrical charges of the floc, fiber, etc.,and/or of the air or gas bubbles has occurred. It is known that when twodifferent materials are in contact, electrons from one material can moveacross the boundary and associate with the other. These electrons alignthemselves near the interface since the first material now has a slightpositive charge. Although the distance between the negative and positivecharges is extremely small, an electrical field and a difference inpotential now exist. The voltage across their "electrical double layer,called the contact" or zeta" potential, is only 0.001 to 0.1 volt.

If the two materials in contact are good conductors of electricity, andare now separated, the excess electrons in one material will return tothe other one before final contact is broken. But if one (or both) ofthe materials is an insulator, this flow will be impeded; if theseparation is done rapidly enough, some of the excess electrons will betrapped in one of the materials. Then both materials will be charged. Ifone of the materials is a grounded conductor it, of course, will notretain its charge, but in the case of a pressurized liquid passing athigh velocity through a valve and being released within the flotationtank proper, the charge of the doc could be changed even though theconductive liquid would transmit the excess electrical "Ice charge tothe ground. This explains why some successful tests carried on with aflotation kit cannot be reproduced with a pilot unit or an industrialunit. It must be understood that the two materials or phases in initialcontact may be two solids, two immiscible liquids, a solid and a liquid,a solid and a vapor or gas, a liquid and a vapor or gas. The importantpoint to keep in mind is that whenever there is contact and separationof phases a charge may be developed that could be disastrous.

In a standard flotation unit, when the pressurized liquid is released inthe flotation tank proper, static electricity could develop in or nearthe release valve itself, at or near the point where a high velocityflow is produced. If the releasing valve and the liquid are goodconductors, change in the charge of the floc may t happen. However, ifthe valve is made of an insulati material like rubber, a change inelectrical charges will happen. This change could improve or harm theattraction between the doc, fibers, etc., and the air or gas bubbles,depending on what the doc charges were, what changes happened to the airor gas bubbles, and what changes happened to the doc itself. Sometimes Ihave even found that a complete destruction of the floc occurs becausewhen the pressurized liquid is released, the floc is broken by theturbulence, as normally happens, but at the same time its electricalcharges as well as the electrical charge of the air or gas bubbles arechanged to the same electrical charge, which means that pieces of flocwould not be attracted between themselves, nor between themselves andthe air or gas bubbles. Actually, they are repelled.

The above difliculties with flotation of floc, fiber, etc., led me to myinvention where Icontrol the electric charges in the flue and or in theair or gas bubbles, which I can do through different approaches: thefirst relies on small bubbles of gas or air coming up from the bottomand in countercurrent with the liquid being clarified, said bubblescarrying one or more chemicals in powder form, which has or have beencharged electrically positively or negatively, according to the demandof the liquid being treated, by using an electrostatic charger 7 whichcharges small par ticles passing through it, negatively or positively,as required and making these charged particles to travel within relativesmall gas or air bubbles through the liquid being clarified. In this waywe accomplish the purpose of a sure adhesion of the bubble to the matterwe want to take out of the liquid, being understood that this matter hasalready been flocculated or is being fiocculated by the chemical carriedby the gas or air bubbles. With this method we overcome the disadvantageof producing static electricity.

It must be understood that the charged powdered chemical particles, willbe electrically discharged as soon as they get in direct contact withthe water. Therefore, the larger the air or gas bubbles, the moreprobabilities for the charged chemical of not being discharged and ofadhering to the floc. However, it is also a fact that the smaller thebubbles the more time the bubble is maintained adhered to the floc.

The second approach is obtained through ionizing the air or gas beingbubbled with a source of radioactivity. The minimum ionization in air isabout .50 ion pairs per cm. of path, and is produced, for example, byelectrons having an energy of the order of 1 mev. Another approach wouldbe by cle'dtromagnetic irradiation associated with sodium vapor lightand the like. A fourth approach would be the use of a plastic orinsulated release valve to partially regulate the increase or decreaseof an electric charge. However, change from positive to negative andvice versa can not be made with this approach. One object of thisinvention is to neutralize any undesirable charge that could be producedduring the release of the pressure of the liquid according to the aboveexplanation.

Another ob ect of the present invention is to give to the air bubble thespecific electrical charge.

A further object of the present invention is to provide simple, durable,and efficient flotation apparatus in which controls are provided tocontrol the amount of electrostatic charge required for a good adhesionto the fioc.

Another further object of the present invention is to provide aselective control to charge positively or negatively the air or gasbubble as required.

The practice of the invention will be best understood by reference tothe accompanying drawings. In the drawings, in the several views ofwhich like parts have been designated similarly;

FIG. 1 is an elevation of one embodiment of this lIlVCll tion.

FIG. 2 is Section A-A of FIG. 1.

FIG. 3 is an elevation of another embodiment of the present invention.

FIG. 4 is an elevation of another embodiment of the present invention.

FIG. 5 is an elevation of still another embodiment of the presentinvention.

FIG. 6 is an elevation of the type of difiuser 5 shown in FIG. 1.

FIG. 7 is a top view of the diffuser shown in FIG. 6.

One embodiment of this invention consists of a circular (but may besquare) tank 1 as shown in FIGS. 1 and 2 with a top skimmer 2 andcollector 3.

From 1 to 3 feet under the skimmer 2 which is driven by a motor 17,there is an inlet distributor 4 to distribute evenly the incomingliquid. At the bottom 6 of the tank 1 there are several gas diffusers 5as shown in FIG. 1, the number of diflusers being dependent on thecapacity of the unit. These difiusers 5 comprise a hollow shaft 70, acentrifugal blower 71, and a circular plate 72 with holes 73.

The hollow shaft 70 is connected to air or gas. The

gas blower 71 is of the centrifugal type and is used to draw gasesthrough the hollow shaft 70 and bubble it in the liquid through itsperipheric outlets. The shape of the blower blades are not describedbecause any suitable centrifugal blower can do the job. The only specialspecification is that said blower must produce a minimum of turbulencein the surrounding liquid.

When the air or gas leaves the peripheric holes of the blower 71 whichis rotating, the gas is divided in small bubbles. Said bubbles tend togo up, finding in their ascending pass the circular plate 72 whichpermits said bubbles to pass through holes 73, but at the same timecutting said bubbles in smaller bubbles so that the final diameter ofsaid bubbles depends on the side of the holes 73 and in the speed atwhich the plate 72 revolves. Between the inlet distributor 4 and the gasdiffusers 5 there are several vertical partitions 9 as shown in FIGS. 1and 2, equally spaced to form vertical square cells in order to avoidunnecessary movement of the liquid within the apparatus and making itable to be sized for any desired capacity without developing of needleshydraulic flows. These walls 9 are attached to the tank wall by anyreasonable means.

The diflusers 5 are connected through the bottom 6 of tank 1 to anelectrostatic charger 7 through piping 8. The electrostatic charger 7has an upper opening 20 through which one or more powdered chemicalsfall in from the feeder hopper 10. The diffusers 5 are driven byelectric motors 11 with a hollow shaft as shown in FIG. 1, or by anyknown system as pulleys, gears, etc. Packing glands l8 and 19 have to beused.

Also at the bottom 6 there are several outlets 12 connected throughpipes 13 and 14 to the clarified liquid collector 15 where the liquidlevel is regulated. From here the clarified liquid goes out of the unitthrough outlet 16.

The electrostatic charger 7 must have controls to regulate the requiredvoltage, and to change from positive to negative or vice versa theelectrical charge added to the chemical or chemicals.

According to the above explanation, I am going to explain how myinvention works:

The liquid to be clarified comes in through inlet distributor 4 andstarts descending. If more than one chemical is added to the liquid, itmay be added before inlet 4, but at least one powdered chemical or aportion of it must be added through the gas dilfusers 5, in order toobtain the electrical charges we need for producing a good equilibriumwithin the liquid and the matter we are trying to eliminate.

At the same time that the liquid is descending, gas or air comes inthrough the opened top 20 of the electro static charger 7, entrainingthe powdered chemical or chemicals falling from the feeder hopper 10,passing through the electrostatic charger 7 where the powdered chemicalis charged with the required charge, continuing through pipe 8 until itreaches gas difiusers 5 from which it passes toward the liquid where itis diffused in small gas or air bubbles carrying the char ed powderedchemicals. The latter starts ascending with e gas or air bubbles andadhering to the matter descending with the liquid until it reachesskimmer 2 which will remove this froth through outlet 3.

The descending liquid will loose all its flocculated or beingflocculated matter proportionally to the coincidence of said matter withcharged particles, then passing between the gas diffusers and reachingoutlets l2, pipes 13 and 14. collector ring 15 and outlet 16. Drain pipe21 will be used in case heavy particle deposit occurred on the bottom 6or for cleaning the unit. A blind flange or a valve must be used.

The vertical partitions 9 could be spaced less than 1 foot apart ifrequired by hydraulic flows. Also, if the inlet dis tributor 4 andoutlets 12 are well designed to produce a good laminar flow and in orderto make smaller the distance between them, the vertical partitions 9 maybe elimi= nated. It must be understood that the chemicals added throughinlet 4 could be in the liquid form if required.

FIG. 3 is a description of another embodiment of the present inventionwhere only the lower part of the unit has been drawn; from the space inFIG. 1 between vertical partitions 9 and circular gas difl'users 5 down.

The diflerences with the embodiment in FIG. 1 are:

Instead of the rotatory gas difluser 5 we have installed anotherdistributor ring 22 which has holes 23 in order to distribute uniformlythe incoming fluid. Underneath this ring there is a cone 24 with ascraper 25 and a hole 26. This cone 24 divides the tank 1 into twochambers, the upper 27 and the lower 28, interconnected by hole 26. Thelower chamber has also a coned bottom 29 with a scraper 30 at the bottomand an outlet 31 at the lower end of said cone 29 and a drain valve 32.At the top of this lower chamber 28 there is a collector ring 33 tocollect the clarified liquid, which is connected through pipe 40 toservice line 35 and pump 34.

After the pump 34, there is an air injector 37 to entrain air or gasfrom the electrostatic charger 7. The air injector 37, pipes 38 and 39,and distributor ring 22 must be made preferably of plastic.

How it works; The liquid to be clarified gets in through distributor 4and starts descending through vertical partitions 9, passes bydistributor ring 22 and continues downward through hole 26 to the lowerchamber 28. There it makes a vertical U-turn and starts ascending untilit reaches the collector ring 33. From here the liquid goes through pipe40 to T 41 where it is divided in two streams. One goes through pip? 35as clarified liquid to service, and the smaller portion goes to pump 34.From here to the air or gas injector 37 where air or gas, mixed with theelec= trical charged chemical or chemicals is entrained and mixed withthe liquid, then continuing through pipe 38. distributor ring 22 andholes 23 toward the upper chamber 27.

After entering chamber 27 the mixed fluids are sepa= rated in the liquidwhich goes downward, repeating the cycle. and the air or gas bubblesthat float and start ascend= mg, attracting the already formed or beingformed doc, and carrying it upward to the skimmer 2 and outside the unitthrough collecter 3. The scrapers 25 and 30 could be of the chain type.The embodiment of FIGS. 1, 2 and 3 are better applied to liquids withrelative high viscosity where large air or gas bubbles can be producedas is currently done in the clarifiers used by some sugar refineries,where they do not produce small air or gas bubbes but relative largebubbles because the probabilities for an electrical charged chemicalfloating within the air or gas bubbles to be discharged by contact withthe surrounding liquid are smaller for a large bubble than for a smallone.

Another embodiment of the present invention is shown in FIG. 4. Thisembodiment is similar to the one shown in FIG. 1, but the bubbles arenot in countercurrent with the liquid being clarified. They both flowupwardly in the same direction.

This apparatus is made up of tank 1 and vertical walls 9 as in FIG. 1,at the bottom has a distributor 46, which in this case not necessarilyhas to be of the same type as described in FIG. I, but could just be astandard distributor or just a pipe with holes to distribute uniformlythe flow, because in this case the bubbles have already been formed bythe ejector 42- At the top of tank 1 there is a circular, vertical wall47 concentric with tank 1 and with holes at the bottom 48 resting on thebottom 49 of an annular tank 50 of a diameter larger than the diameterof tank 1, and with outlets 51. Also at the top of the tank 1, there isthe skimmer 2 with its overflow 3 and electric motor 17. Above bottom 6,there is the pipe 43 to connect the distributor 46 to ejector 42. Thelatter is connected through pipe 44 to the electrostatic charger 7 withits feeder hopper 10, and through pipe 45 to the liquid being treatedwhich must have enough pressure to make the ejector 42 work. Ejector 42and pipes 45, 44, and 43, and distributor 46 must be made of plastic orother insulating material.

How this embodiment works: After mixing the liquid being treated withone or more chemicals as required and which must be at the minimumpressure required by the ejector 42 to work properly, the same will flowthrough pipe 45 and ejector 42 where it will draw air or gas and formbubbles. As explained in relation to FIG. 1, this air or gas entrainsone or more electrostatic charged chemicals. Thus, when the air or gasbubbles are formed, they carry with them some of the electrostaticallycharged powdered chemical which makes the air or gas bubble to be anegatively or postively charged bubble. Other chemicals, if needed, havebeen added to the liquid and have flocculated or started to flocculatewhen they arrive to the ejector 42. Therefore, if the electrostaticcharge of the powdered chemical being entrained by the air or gas hasbeen properly charged, it will be attracted toward the floc whileflowing through pipe 43 and distributor 46 and into the liquid insidethe lower part of tank 1. Then, the liquid being treated and the flocand air or gas bubbles will ascend through walls 9 until reaching thetop 52 of the tank 1 proper. At this point the fine and air or gasbubbles continue its upward movement. However, the liquid will flow overthe top 52 toward the circular vertical wall 47 with a horizontal flow,which helps in separating the floc from the liquid proper. The circularwall 47 with its holes 48 at the bottom, forces the liquid to traveldownwardly until passing through holes 48 and entering in the outercircular ring-type chamber 53 where is located the outlet 51 which hasmeans with vertical movement in order to regulate the liquid level ofthe apparatus. The H and air or gas bubbles that keeps moving upwardly,accumulate at the top of the liquid and form a float which is pushedtowards the outlet 3 by the skimmer 2.

Still another embodiment of the present invention is the application ofthe principle of the electrostatic charger to a standard flotationclarifier like the one shown in FIG. or similar unit. This embodimentrefers to a unit for separating solids is floc and fiber from liquids,of the type wherein the suspension is caused to flow substantially in ahorizontal direction, through a separating container 64 which is openedat the top and is made of four exterior verical walls of which 62 and 63correspond to the end vertical walls and a horizontal plane bottom 56.It is provided with an inlet opening 58 in the end wall 62 for theliquid to be purified and an outlet opening 66 at the bottom and nearthe end wall 63. Within the above container there are three verticalbaffles 59, 60 and 67. At the top of the separating container there is askimmer assembly 68 with paddles 61 and an inclined plane 69 at the leftend of FIG. 5, to take off from the liquid the floating floc or fiber.At the right of FIG. 5 there are an ejector 55, a pump 34 and theelectrostatic separator 7 with its feeder hopper 10.

How it works: The liquid that is going to be treated is mixed with thenecessary chemical or chemicals except for one chemical or part of itwhich is fed through the electrostatic separator 7 as expki d inrelation to FIGS. 3 and 4. After the above mention mixing, it is fedthrough pipe 54 to the pump 34 and ejector 55. The pump 34 gives to saidliquid the minimum pressure required to make work the ejector 55. Theejector 55 draws air or gas mixed with one electrically charged powderedchemical from the electrostatic charger 7, and the air or gas is bubbledin the liquid where floc formation is taking place. If the right chargewas added to the bubbles a good adhesion of floc and bubbles will takeplace and after flowing in the flota tion unit proper 64, the liquidwill pass over baflle 59 and the floc will float and separate from theliquid. After ar riving the floating floc or float at the liquid toplevel, it will be pushed toward the incline plane 69 by the paddles 61and out of the unit through proper means. The liquid left in the unitwill run toward wall 60 and will pass under it, then due to the battle67 it will have to pass over it and fall down toward outlet 66 and outof the unit through pipe 65. It will be obvious to one skilled in theart that various changes may be made in the invention without departingfrom the spirit and scope thereof and therefore, the invention is notlimited by those which are illustrated in the drawings and described inthe specifications.

What is claimed is:.

1. A method for clarifying liquid[-] containing matter to be removedtherefrom, said matter being selected from the group consisting of floc,fibers, partially or totally formed floc, and partically or totallyflocculated fibers, said method comprising the steps of:

Lintroducing into said liquid a flow of gas bubbles having containedwithin the individual bubbles at least one powdered chemical particlehaving an electrical charge of the opposite polarity as the matter to bere moved from the liquid to be clarified, said powdered chemical alsobeing a flocculating agent for the matter to be removed in the eventsaid matter to be removed is not otherwise flocculated;

2.providing means to insure uniform mixing of said gas bubblesthroughout said liquid to be clarified: and

3. subsequently removing from the surface of said liquid theconglomerate formed by adherence of said now flocculated matter to beremoved from said liquid with the powdered chemicals introduced intosaid liquid in said gas bubbles, thus leaving a clarified liquid behind.

2. The method of claim 1 wherein said powdered chemi cals are providedwith the proper electrical charge by an electrostatic charger.

3. The method of claim 2 wherein the flow of gas bubbles iscountercurrent the flow of liquid being clarified of matter.

4. The method of claim 1 wherein said matter to be removed from saidliquid is partially or wholly flooculated at the time of theintroduction thereinto of said powdered chemical-containing gas bubbles.

(References on following page] 7 References Cited The followingreferences. cited by the Examiner, are of record in the patented file ofthis patent or the original patenti UNITED STATES PATENTS 8 147,1179/1964 Halton .W 210-44 3,479,281 11/1969 Kikindai et a1 210- 4 US. Cl.X.R,

204-149; Z09166; 210---22lo THOMAS G. WYSE, Primary Examiner

1. INTRODUCING INTO SAID LIQUID A FLOW OF GAS BUBBLES HAVING CONTAINEDWITHIN THE INDIVIDUAL BUBBLES AT LEAST ONE POWDERED CHEMICAL PARTICLEHAVING AN ELECTRICAL CHARGE OF THE OPPOSITE POLARITY AS THE MATTER TO BEREMOVED FROM THE LIQUID TO BE CLARIFIED, SAID POWDERED CHEMICAL ALSOBEING A FLOCCULATING AGENT FOR THE MATTER TO BE REMOVED IN THE EVENTSAID MATTER TO BE REMOVE IS NOT OTHERWISE FLOCCULATED;
 2. PROVIDINGMEANS TO INSURE UNIFORM MIXING OF SAID GAS BUBBLES THROUGHOUT SAIDLIQUID TO BE CLARFIED; AND
 3. SUBSEQUENTLY REMOVING FROM THE SURFACE OFSAID LIQUID THE CONGLOMERATE FORMED BY ADHERENCE OF SAID NOW FLOCCULATEDMATTER TO BE REMOVED FROM SAID LIQUID WITH THE POWDERED CHEMICALSINTRODUCED INTO SAID LIQUID IN SAID GAS BUBBLES, THUS LEAVING ACLARIFIED LIQUID BEHIND.